Tue, January 11, 2022 Turnagain Pass Avalanche Forecast

Tue, January 11th, 2022

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

2 - Moderate

0 - No Rating

1 - Low

2 - Moderate

3 - Considerable

4 - High

5 - Extreme


Travel Advice	Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.	Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.	Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential.	Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.	Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches	Natural and human-triggered avalanches unlikely.	Natural avalanches unlikely; human-triggered avalanches possible.	Natural avalanches possible; human-triggered avalanches likely.	Natural avalanches likely; human-triggered avalanches very likely.	Natural and human-triggered avalanches certain.
Avalanche Size and Distribution	Small avalanches in isolated areas or extreme terrain.	Small avalanches in specific areas; or large avalanches in isolated areas.	Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.	Large avalanches in many areas; or very large avalanches in specific areas.	Very large avalanches in many areas.

Recent Avalanches

Seward Highway/Portage Valley: Multiple natural avalanches were observed in the paths along the road near Girdwood and in the Portage Valley. Avalanches were running about 75% of the way to the valley bottom.

Seattle Ridge: Riders reported triggering multiple small storm slabs near the motorized uptrack. Nobody was caught in any of the slides.

Storm slab avalanche on a steep rollover near the Seattle Ridge uptrack. Photo submitted anonymously. 01.10.2022

Avalanche Problem 1

Wind Slabs
Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

Size

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Likelihood of Avalanches

Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches

Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word	Size (D scale)	Simple Descriptor
Small	1	Unlikely to bury a person
Large	2	Can bury a person
Very Large	3	Can destroy a house
Historic	4 & 5	Can destroy part or all of a village

More info at Avalanche.org

The heavy snow and strong winds from yesterday have buried a variety of weak surfaces, which will keep avalanche danger elevated today. As of 6:00 this morning, storm totals are as follows:

Alyeska: 15-18″ snow equalling 1.5-2.1″ snow water equivalent (SWE)
Turnagain Pass: 10-12″ snow equalling 1.1″ SWE
Summit Lake: 3″ snow equalling 0.2″ SWE

Storm totals were higher in the Portage and Placer valleys. which likely recieved 18+” in the upper elevations. This snow came along with strong easterly winds through most of the day yesterday. The Sunburst weather station recorded sustained speeds of 20-50 mph with gusts of 35-70 mph through 6:00 p.m. Winds in the Girdwood area were slightly calmer at 15-20 mph before dropping down to around 10 mph at 11:00 a.m. yesterday. While we are expecting to see precipitation trickle off today, the problem we are left dealing with is that all of yesterday’s storm snow has buried a variety of weak surfaces that will remain reactive today. This includes a layer of near-surface facets that formed during the cold and clear weather in the first week of the year, pockets of buried surface hoar that formed just before this storm moved in, and the New Year’s rain crust that is buried anywhere from 1-3′ deep in the mid and upper elevations.

Since the new snow is burying these persistent weak layers, we can expect to see sensitive avalanche conditions lingering a little bit longer than normal following this storm. The most likely place to trigger an avalanche will be on steep slopes that have been recently wind loaded. The most suspect locations will be above treeline, near ridgelines, below steep convexities, and in gullies. It may also be possible to trigger an avalanche up to a foot deep on steep slopes sheltered from the winds in the middle elevations. Traveling in the mountains today will require an extra alertness. Seek out feedback as you move around. Look for clear signs of poor stability like shooting cracks, collapsing, and fresh avalanche activity like John mentions in his video from the field below. The current snowpack will need more time to adjust, and today is not a good day to jump out into big terrain.

Loose Wet avalanches: Continued light rain up to 1200-1500′ as of 6:00 this morning will make it likely we will see some loose wet activity in the lower elevations. These avalanches will most likely be relatively small and slow moving, but they can have consequences if they push you into terrain traps like alders, trees, creeks, or rocks. As always, be sure to pay attention to the terrain above you so you don’t get caught off guard.

Shooting cracks at treeline in the Tincan trees yesterday. Since this storm fell on weak surfaces we can expect to see similar signs of poor stability lingering on some slopes today. Photo: Mike Loso. 1.10.2022.

Weather

Tue, January 11th, 2022

Yesterday: A warm and wet storm brought 10-12″ snow (1.1″ SWE) to Turnagain Pass, 15-18″ snow (1.49-2.09″ SWE) to Girdwood, and almost missed Summit Lake entirely, dropping only 1-2″ snow (0.2″ SWE). Strong easterly winds were blowing 20-50 mph, gusting 35-70 mph at Turnagain Pass until calming down around 6:00 p.m. Girdwood stayed slightly calmer at 15-20 mph with gusts of 30-60 mph before dropping to 5-15 mph with gusts around 15-30 mph since 11:00 a.m. yesterday. Temperatures have been in the upper 20’s to low 30’s F since yesterday morning. Mixed snow and rain has made it up to 1500′ in Girdwood and around 1300′ in Turnagain Pass.

Today: Light snow with rain to 1200′ is expected to subside this morning, with breaks in the clouds possible later this afternoon. We may see another 1-2″ snow before this round ends, with temperatures dropping in the mid 20’s F by the end of the day into tonight. The rain level is expected to drop back down to 500-600′, and light southeasterly winds are expected at 5-10 mph with gusts of 10-15 mph.

Tomorrow: Snow showers are expected to resume tonight, with another 2-5″ expected by the end of the day tomorrow. Right now it is looking like Turnagain Pass will be on the low end of that estimate and Girdwood will be on the upper end. Easterly winds are expected to pick up overnight into tomorrow at 15-30 mph under cloudy skies. Overnight low temperatures are looking to be in the low to mid 20’s, with daytime highs in the mid 20’s to low 30’s. Rain level is expected to stay around 300-800′.

PRECIPITATION 24-hour data (6am – 6am)

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	33	3	0.4	72
Summit Lake (1400′)	30	1	0.1	24
Alyeska Mid (1700′)	33	4	0.72	47

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	ENE	17	60
Seattle Ridge (2400′)	28	SE	9	25

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/13/24	Turnagain	Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South	H Thamm
05/13/24	Turnagain	Observation: Turnagain Pass non-motorized side	Amy Holman
05/12/24	Turnagain	Observation: Warm up Bowl	Tony Naciuk
05/07/24	Turnagain	Observation: Turnagain Pass Wet Slabs	A S
04/29/24	Turnagain	Avalanche: Turnagain aerial obs	Tully Hamer
04/27/24	Turnagain	Observation: Johnson Pass	Noah Mery
04/23/24	Turnagain	Observation: Turnagain Sunny Side	Travis SMITH
04/21/24	Turnagain	Observation: Bertha Creek	Anonymous
04/20/24	Turnagain	Avalanche: Spokane Creek	Schauer/ Mailly Forecaster
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster

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